The 1st Royal Oak styles ended up equipped with the calibre 2121 motion, which was dependant on the calibre 2120 created by Audemars Piguet in 1967, the globe’s thinnest self-winding movement in the period with day indicator, and an Over-all height of three.05mm. The calibre 2121 was also equipped using https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/